Fluid actuated down-hole pump

ABSTRACT

A short down-hole fluid actuated pump assembly which includes a valve assembly, an engine, and a production pump. The valve assembly receives a source of power fluid from the surface of the earth. The production pump is reciprocatingly actuated by means of the engine which in turn receives a source of power fluid through the valve assembly. A piston, having a passageway formed therethrough, is connected to a hollow valve control rod and to a pump connecting rod. A seal tube receives the control rod therewithin and includes a seal means which isolates the tube from a power fluid inlet to thereby form a path of fluid flow from the valve assembly, to the seal tube, into and through the control rod, and to the bottom of the piston. This expedient substantially increases the permissible size of the piston with respect to the outside diameter of the engine cylinder while at the same time effectively shortens the length of the pump.

O United States Patent 1191 1111 3,865,516 Roeder [45] Feb. 11, 1975[54] FLUID ACTUATED DOWN-HOLE PUMP [76] Inventor: George K. Roeder, Box4335, [57] ABSTRACT Odessa Tex 79760 A short down-hole fluid actuatedpump assembly [22] Filed: Aug. 3, 1973 which includes a valve assembly,an engine, and a production pump. The valve assembly receives a source[21] Appl' No" 385459 of power fluid from the surface of the earth. Theproduction pump is reciprocatingly actuated by means of [52] U.S. Cl.417/403 the engine which in turn receives a source of power [51] Int.Cl. F04b 17/00 fluid through the valve assembly. A piston, having a [58]Field of Search 91/319, 225, 403; 417/403, passageway formedtherethrough, is connected to a 417/404, 399 hollow valve control rodand to a pump connecting rod. A seal tube receives the control rodtherewithin [56] References Cited and includes a seal means whichisolates the tube from UNITED STATES PATENTS a power fluid inlet tothereby form a path of fluid flow from the valve assembly to the sealtube into and ,081,223 51937 C b l 417 404 119,736 6/1938 cgbgll 91/31/9 x through tho Control foo, and to the bottom of the Pls'2,204.12() 6/1940 Coben), 417/404 X ton. This expedient substantiallyincreases the permis- 3,540,814 11/1970 Roeder 417/399 sible size of thepiston with respect to the outside di- Prmary Examiner-William L. FreehAssistant Examiner-Gregory Paul LaPointe Attorney, Agent, or Firm-MarcusL. Bates ameter ofthe engine cylinder while at the same time effectivelyshortens the length of the pump.

6 Claims, 10 Drawing Figures PMENTEUB' HWS Fna 1 FLUID ACTUATEDDOWN-HOLE PUMP BACKGROUND OF THE INVENTION The present invention relatesto down-hole fluid operated pump assemblies, sometimes called hydraulicpumping units. "Fluid operated pump systems do not require areciprocating sucker-rod string such as used by conventional pumps, forexample, in order to transmit the necessary force for the pumping actionfrom the surface ofthe ground to the bottom hole pump. The pump systemof the present invention generally requires a high pressure hydraulicpump which is located above the surface of the earth and whichrecirculates a portion of the produced fluid from the well back to thepump assembly located down-hole in the well. A valve assemblyinterconnects the high pressure fluid source with the engine of the pumpassembly to move a pump connecting rod which in turn enables fluid to beforced from a production zone to the surface of the earth. This state ofthe art is adequately described in my prior U.S. Pat. Nos. 3,453,963;3,517,714; 3,540,814; 3,625,288; 3,650,640, and 3,703,926; as well as inthe prior art patents to C. .1. Coberly; namely, U.S Pat. Nos.2,081,223; 2,230,830; and 2,338,903; to which reference is made for someof the operational details of the pump assembly.

As pointed out in my Us. Par. No. 3,540,814 the various prior artdevices presently available include an engine or motor end, and it iscommon practice to conneet two production ends, or pumps, to one powerpiston. ln hydraulic pumping units of the type used in deep wells, theoperating pressure requirements of the engine increases in proportion tothe required hydrostatic head. On deep wells the pressure requirementssometimes reach a magnitude wherein further increase in operatingpressure in order to attain a deeper well setting results in pumpfailure. Since the maximum operating pressure to which an engine of thepresent invention can be subjected is limited, the only remaining designexpedient available in order to extract more power from the surfacehydraulic pump is to increase the area and stroke of the piston locatedwithin the engine which drives the pump. This latter expedient has theobvious limitation of the physical size of the piston which can belocated within the cylinder of an engine. In U.S. Pat. No. 3,540,814there is set forth a downhole pump having an engine which enables anincrease in the physical size of the piston which imparts an increasedlifting force into the production pump. However, the improved pump is ofexcessive length for some pump cavities and accordingly, it is desirablethat the pump length be shortened by providing the pump engine withimproved design expedients which effectively attain this goal withoutlosing the advantages of increased piston and cylinder area.

SUMMARY OF THE INVENTION The present invention relates to a down-holefluid actuated pump assembly for use in lifting fluids from a fluidproducing stratum associated with a well by utilizing hydraulic power orfluid provided from the surface ofthe ground and suitably conveyed to anengine associated with the pump assembly. The pump assembly generally iscomprised of-an elongated cylindrical unit having an upper end connectedto a power fluid source, an outlet connected to a produced fluid flowconduit, and a pump inlet connected to or in communication with thefluid producing stratum. This arrangement enables the fluid produced bythe stratum to be lifted to the surface of the earth along with thespent power fluid from the engine.

The present invention advantageously permits an increased diameter ofpiston to be utilized in the engine by eliminating the heretoforerequired flow passageways located within the cylinder wall within whichthe engine piston reciprocates. The expedient is brought about by theprovision of a hollow pilot valve rod having a free marginal end portionreciprocatingly received within a seal tube in a manner to form a flowpassageway to the underside of the engine piston while the remainingupper side of the engine piston is flow connected to the valve means bya flow passageway located above the portion of the engine cylinderwithin which the piston reciprocates. Hence, the present inventionenables a reduction in the overall length of the pump assembly as wellas eliminates the necessity for conducting fluid flow through the wallwhich forms the engine cylinder, thereby enabling a larger cylinder boreto be incorporated within the engine than would other wise be possible.

Therefore, a primary object of this invention is to provide the engineof a down-hole pump assembly with means for increasing the piston areathereof so that power fluid can apply increased force to actuate aproduction pump, while at the same time the overall length of the engineis effectively reduced.

Another object of this invention is to provide a short down-hole pumpassembly with an engine which utilizes a continuation of the housing ofthe fluid actuated pump as the engine cylinder.

A further object of the present invention is the provision of an engineassociated with a fluid operated pump assembly which eliminates thenecessity of passageways being formed within the cylinder wall oftheengine assembly, and which can be used in a standard pump cavlty- Stillanother object of the present invention is the provision of improvementsin seal means for a hollow valve control rod which is utilized to conveypower fluid to one side of an engine piston. j

A still further object of the present invention is the provision of pumpapparatus which enables an improved, more powerful engine to be designedwhich can be utilized with existing valve assemblies and productionpumps in order to increase the lifting power of a down-hole hydraulicpump assembly.

Still another object of the present invention is the provision of animproved fluid path for a down-hole pump assembly of either the free orthe fixed type.

A still further object of the present invention is to provide animproved fluid flow path for the engine of a down-hole pump whichpermits the maximum size piston to be used by elimination of flowpassageways from the cylinder walls, and which permits a substantialreduction in the length of the pump assembly.

Still another object of the present invention is the provision of a flowsystem for the engine of a downhole pump which enables reduction in thelength of the engine.

The above objects are attained in accordance with the present inventionby the provision of a fluid operated pump assembly fabricated in amanner essentially as outlined in the above summary and abstract. Otherobjects and advantages will become apparent to those skilled in the artas the details of construction and operation are hereinafter more fullydescribed and claimed.

BRIEF DESCRIPTION OF THE DRAWINGSA FIG. I is a longitudinal,fragmentary, part crosssectional view of an improved fluid actuated pumpassembly which has been fabricated essentially in accordance with thepresent invention with the pump assembly being disclosed in one of itsoperative configurations;

FIG. 2 is an enlarged, fragmentary, longitudinal, cross-sectionalrepresentation of the present invention;

FIG. 3 is an enlarged, fragmentary, longitudinal, cross-sectional viewof one embodiment of the invention disclosed in FIG. 2;

FIG. 4 is a cross-sectional View showing the apparatus of FIG. 3 as itappears when in a different operative configuration;

FIG. 5 is a broken, enlarged, longitudinal, crosssectional view of adetail of a fluid actuated pump assembly made in accordance with thepresent invention;

FIG. 6 is a cross-sectional view of the apparatus disclosed in FIG. 7;

FIG. 7 is a detailed, enlarged, side elevational view of part of theshort bottom hole pump made in accorodance with the present invention;

FIG. 8 is an enlarged, cross-sectional view illustrating the details ofthe apparatus disclosed in FIG. 9;

FIG. 9 is a detailed, enlarged, side elevational view of theillustration seen in FIG. 8; and,

FIG. l0 is an end view of the apparatus disclosed in FIG. 8 and 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. l the arrow atnumeral l0 broadly illustrates a short bottom hole pump located downholein a borehole. The borehole is cased at l2 so that a seating shoeassembly can be operatively installed adjacent to a production zone. Asurface return tubing 16 returns produced and spent power fluid to thesurface of the earth. Production fluid at 18 enters a standing valveassembly 20 and flows into the hydraulic pump assembly located withinpower tubing 22.

The pump assembly y24 is of the free type and therefore includes apacker nose assembly 26 having a check valve stem 28 located immediatelyabove the illustrated inlet ports which in turn are located above theillustrated spaced packer cups 30. Packer connector 32 connects the noseassembly to the remainder of the pump assembly by means of an extensionnipple 34. Seal tube 35 is axially positioned within the extensionnipple and forms an annular settling chamber 36 therewith.

Power fluid inlet ports 37 are located above a standard 0-ring sealcollar 38 while spent power fluid exhaust 39 are located below the0-ring seal collar in the usual manner.

The hydraulic pump assembly includes an engine valve assembly 40connected to an engine cylinder assembly as indicated by the numeral 42in FIG. 2. Production exhaust ports 43 and 45 are spaced above and belowa production end 44 of the pump assembly, the details of which are setforth in U.S. Pat. No. 3,540,814.

As seen in the illustration of FIG. 2 -4, in conjunction with FIG. 1,wherein so far as is possible, like numerals refer to similar or likeelements, the before mentioned power fluid inlet 37 can be arranged inthe alternate position seen illustrated at 46 in FIG. 4,as may berequired for conventional type pumps. The upper extremity of the enginevalve assembly is preferably threaded at 48 to provide for attachment toa power tubing string. The sub 50 can be changed to packer connector asillustrated in FIG. 2 as may be desired. The main body 49 of the valveassembly threadedlyengages the spaced upper and lower subs 50, 5l.Longitudinally extending hollow valve control rod 52 is provided withthe illustrated spaced flats 53; 53' thereon with the marginal free endportion of the rod being freely and reciprocatingly received within theinterior of the before mentioned seal tube, while the remaining or fixedend of the rod is threadedly connected to an engine piston 54. Thepiston divides the engine cylinder into upper and lower cylinderchambers 55, 56 respectively. Annular downwardly opening passageway 57interconnects the first longitudinally disposed passageway 58 with theupper cylinder chamber by means of member 59, which is removably affixedto the lower sub member. Control sleeve 60 is supported by and isaffixed to member 59 and sealingly engages the reciprocating pilot rodin a slidably sealed relationship therewithin, as will be explained ingreater detail later Port 6l communicates annulus 62 with port 63 whichin turn is flow connected to passageway 64 and to the exhaust port 39.Upper and lower ports 65 and 65', respectively, are formed within thesleeve. Port 65' communicates annulus 66 with annulus 62 by means offlat 53 when the sliding valve 67 is in the upper position. Variableannulus 69 is flow connected to upper port 65 by the upper flat 53' whenthe control rod is in a lowermost position. Sliding valve assembly 67 isprovided with radial ports 68 which communicates annulus 69 and 70 withflow passageway 168.

Reciprocating annulus 7l is formed between the spaced enlargements ofthe sliding valve assembly, one of which is seen at 72. Port 73communicates with annulus 74, while annulus 75 is separated from annularpassageway 70, 74, and 76, while the latter are always in communicationwith one another. Annulus 75 is flow connected to passageway 168 and 77.

The longitudinally extending axial bore of the valve i body accordinglyis comprised of small bore 79 which preferably is inthe form ofa sealsleeve 97 as seen illustrated in FIG. 5, for sealing engages the pilotrod and preventing flow of fluid between power fluid inlet 76 and sealtube chamber 78. The axial bore enlarges at 79' and again at 80 to formthe before mentioned annulus 74 and 76. Within the large counterbore 80there is slidably received in a reciprocating manner the upper marginalend portion of the sliding pilot valve assembly. Ports 73 facilitatesflow into ports 82, which is flow connected to passageway 58, which inturn communicates with annular passageway 57.

The upper extremity 83 of the sliding valve assembly is abuttinglyreceived against shoulder 84. Spaced shoulders 86, 87 form the beforementioned traveling annulus 7l, while spaced relatively movable shoulder88, 89 when spaced or stroked apart as in FIG. 3, form annulus 69therebetween.

Flat 90 forms a flow path which enables flat 53 to communicate annulus66 with exhaust port 6l. Flat 90 further enables flat 53 to form a tlowpath from annulus 66, flat 90, port 65, flat 53' to power fluid annulus70. Sleeve 60 sealingly engages the rod along the area indicated by thenumeral at 91 so as to prevent fluid flow thereacross.

As seen in the detailed embodiment of FIG. 5, seal tube 35 isconcentrically received within its extension nipple 134. Retainerbushing 93 is connected to the upper adapter 92 and freely receives thepilot rod (not shown) therewithin with the pilot rod being received inclose tolerance relationship at axial passageway 99 formed within theseal sleeve 97. The adapter is provided with threads at 98 so that itcan threadedly engage the upper end of a valve body in a manner similarto the illustration of FIG. 2.

In operation, the pump is run downhole on a tubing string, oralternatively, if it is of the free type, the pump may be pumpeddownhole in a manner known to those skilled in the art, and as morefully explained in my U.S. Pat. No. 3,540,814.

Power fluid enters inlet port 37 or 46, depending upon the configurationof the particular embodiment, and flows into annulus 76, 70, and 69; andthrough ports 68, 68'; where the flow can proceed in accordance with therelative posiiton of the sliding valve element. Assuming that thesliding valve element is in the illustrated position of either FIGS. 2or 3, the flow from the variable annulus 69 can proceed through ports68, 63, and into passageway 168; annulus 75; passageway 77; seal tubeannulus 78; and into the interior of the pilot or control rod where theflow continues on down through the rod, through the engine piston, andinto lower cylinder chamber 56 thereby forcing the piston to move in anupward direction carrying the pilot rod therewith. At the same timespent power fluid exhausts from upper cylinder chamber 55, and flowsthrough annulus 57, into the longitudinal flow passageway 58, where thefluid emerges through port 82, flows through traveling annulus 71, andout through exhaust port 39.

As the engine piston upstrokes and nears its uppermost position, thelowermost flat 53 interconnects annulus 66 and 62 by means of ports6land 65', causing reduced fluid pressure within annulus 66 because ofexliaustl passageway 64 being flow connected thereto, thereby drivingthe sliding valve element in a downward dir etionwdue toit-hempressuiedifferential ofthe fluid pressure thereacross.

As the sliding valve assumes the illustrated position of FIG. 4, powerfluid must now flow from annulus 76, through radial port 82, firstlongitudinal passageway 58, and into engine upper annulus 57 where thepower fluid is effected in upper piston chamber 55, thereby driving thepiston in a downward direction. At this time the spent fluid is free toflow from lower chamber 56, through the passageways in the piston,through the interior of the pilot rod, through seal tube annulus 78,passageway 77, into annulus 75, through passageway 168, into travelingannular chamber 7l, and out through exhaust ports 39.

As the piston approaches its lower limit of travel, uppermost flat 53 isbrought into position to interconnect port 65 with annulus 70 therebycausing the control valve element to be shifted into its uppermostposition because of the pressure differential thereacross, therebycausing the engine piston to again reverse its direction of travel. Thepump assembly has now been returned to the configuration seenillustrated in FIGS. 2 and 3. Hence it will now be appreciated that thetraveling valve element 72 alternately connects a first and second flowpassageway to power fluid and exhaust port, with the first and secondflow passages being flow connected to the upper and lower cylinderchambers` so that the engine piston reciprocates with a double action.

By the provision of a seal 79 located between the power fluid chamber 76and the seal tube chamber 78, the distance between the 0-ring sealcollar and the seating shoe assembly is effectively shortened therebyenabling the pump assembly to be used in a standard pump cavity. Thisexpedient enables the packing box heretofore located in underlyingrelationship respective of the valve assembly to be relocated above thevalve assembly, thereby reducing the length of the valve end engine aproportionate amount.

Ari important contribution to the improvement in the pump assembly liesin the novel design expedients incorporated into the control bushing 60and the traveling valve element 67. It will be noted in the embodimentsof FIGS. 2-4 and 6-10 that the bushing sealingly engages the control rodwhile the traveling valve element sealingly engages the axial bore ofthe valve assembly housing. The interior of the traveling valve elementis provided with the illustrated spiral groove 267 which forms a smallcontrolled pressure relief flow passageway in order to prevent the valveelement from becoming locked into an intermediate position. The spiralcommences at the lower terminal end of the valve element and extendsslightly past ports 68, thereby leaving area 167 for sealingly engagingthe control sleeve when the valve element is in the lowermost position.

When the valve 67 is in the position seen illustrated in FIG. 3, thespiral groove 267 provides a controlled supply of power fluid fromchamber 69 into the charnber 66 thereby overcoming any pressuredifferential effected across the valve element due to leakage of powerfluid from chamber 66 through the seal formed between the control rodand the control sleeve. For example, high pressure fluid flow occursfrom chamber 66, through ports 65, 65', along the exterior surface ofthe control rod, through passageway 61, into chamber 62, and then intothe exhaust passageway 64 by means of port 63.

When the valve element is shifted into the position seen illustrated inFIG. 4, the seal area 167 of the valve element theoretically preventshigh pressure fluid from flowing from passageway 70, along the spiralgroove, and under the valve element where premature movement of thevalve element could otherwise be effected by the presence of the highpressure fluid leakage. In actual practice, especially when the valveassembly has become worn through long time in service, it has been foundexpedient to overcome this potential problem associated with the fluidleakage by the provision of a relatively small bleed port 68 whichbleeds any fluid leakage into the exhaust passageway by intersecting theflow path of the leakage, so that, fluid flow from 70 across sealsurface 167 will follow the path of least resistance which is throughports 68, into port 68', and into the exhaust passageway 168. It will benoted that port 68 is closed when the valve element is shifted into itsupper position, as seen illustrated in FIG. 3. Hence, port 68 iscompletely shut off to high pressure fluid flow instantaneously with thespiral groove being opened to a source of high pressure fluid flow uponthe initial upward movement of the traveling valve element.

Flat 90 flow communicates the exterior surface of the control bushingbetween apertures 65, 65 to enable power fluid to more efficiently flowacross the control rod flat when chamber 66 is flow connected to eitherthe exhaust or to the power fluid port,

Shoulders 86 and 87 provide for part of the traveling annulus foralternately connecting together the exhaust and second flow passageway,and the exhausttand first flow passageway.

I claim:

1. A fluid actuated pump assembly having a valve assembly, a power fluidchamber, an engine, and a production pump, a formation fluid inlet flowmeans and a produced fluid flow means flow attached to said pump; meansby which a source of power fluid can be flow connected to the powerfluid chamber of the valve assembly; and a spent power fluid outlet; theimprovement comprising:

said engine having a piston reciprocatingly received within an enginecylinder, said piston dividing said engine cylinder into an uppercylinder chamber and a lower cylinder chamber; a valve control rodhaving an axial flow passageway formed therethrough, said control rodbeing connected to 'said piston and extending through the valve assemblyfor controlling the action of the valve assembly which in turn controlsthe fluid flow path to said engine; a seal tube supported by said valveassembly and spaced from said control rod, said control rod beingreceived within said seal tube; seal means reciprocatingly receivingsaid control rod therethrough for preventing power fluid flow from thepower fluid chamber, along the exterior surface of the rod, and intosaid seal tube; a connecting rod connected between said piston and theproduction pump for actuating the production pump;

means forming a first flow passageway from-the valve assembly to saidupper cylinder chamber, means forming a second flow passageway from thevalve assembly to the interior of said seal tube, and into the interiorof said hollow valve control rod,

through said piston, and into said lower cylinder chamber; means formingan exhaust flow passageway through which spent power fluid from theengine can flow;

said valve assembly includes a control sleeve axially aligned with andreciprocatingly receiving said control rod therethrough;

a valve element concentrically arranged respective to said control rodand said control sleeve and movable from a first to a second position, amarginal length of said control sleeve being received within a marginallength of said valve element;

spaced shoulders on said valve element forming a traveling annulus forflow connecting said exhaustv passageway to said second passageway whensaid valve element is in the first position, and for flow connectingsaid exhaust passageway to said first passageway when said valve elementis in the second position;

a spiral groove formed on a marginal longitudinal interior surface ofsaid valve element which slidably contacts said marginal exteriorsurface of said control sleeve to provide for a bleed passageway throughwhich power fluid can flow;

so that said valve assembly connects said first flow passageway to saidexhaust flow passageway for conducting spent power fluid away from saidupper chamber; and to conduct power fluid flow to said second flowpassageway in order to cause said piston to reciprocate in a firstdirection; and, said valve assembly connects said first flow passagewayto conduct power fluid flow to said upper chamber and to conduct spentpower fluid flow away from said second flow passageway in order to causesaid piston to reciprocate in a second direction.

2. The pump assembly of claim l, wherein said control sleeve has a lowermarginal length thereof supported by said valve body, said lowermarginal length sealingly engaging an outer marginal length of saidcontrol rod for preventing fluid flow from said upper cylinder, alongthe exterior surface of the rod, and into said valve assembly.

3. A fluid actuated pump assembly comprising a valve assembly, a fluidactuated engine, and a production pump;

said valve assembly providing flow control means for said engine andincluding a valve body, a traveling valve element reciprocatinglyreceived within said body and movable between a first and second flowcontrol position, an axial passageway formed through said valve element;

said engine having a cylinder, a piston reciprocatingly received withinsaid cylinder and forming upper and lower cylinder chambers; a valvecontrol rod attached to said piston and having a marginal free endportion extending through said axial passageway, a power fluid flowpassageway formed between said rod and said valve element; means forminga power fluid inlet which is in flow communication with said power fluidflow passageway;

a seal tube for reciprocatingly receiving a free marginal length of saidcontrol rod and forming a flow passageway therebetween;

a seal means separating said power fluid flow passageway from said sealtube flow passageway, a flow passageway formed from said power fluidflow passageway to said seal tube flow passageway;

said valve control rod having means associated with said power fluidflow passageway for causing said valve element to assume said first flowposition and said second flow position in response to reciprocation ofsaid piston;

said valve assembly includes a control sleeve axially aligned with andreciprocatingly receiving said control rod therethrough;

said valve element being concentrically arranged respective to saidcontrol rod and said control sleeve with a marginal length of saidcontrol sleeve being received within a marginal length of said valveelement;

spaced shoulders on said valve element forming a traveling annulus forflow connecting said exhaust passageway to said second passageway whensaid valve element is in the first position;

said valve element is provided with a spiral groove on the marginallongitudinal interior surface which slidably contacts said marginalexterior surface of said control sleeve to provide for a bleedpassageway through which power fluid can flow;

a flow passageway means flow connecting said upper cylinder chamber withsaid valve element; a flow passageway means flow connecting said sealtube flow passageway with said valve element; an exhaust flow passagewaymeans connecting said valve element to exhaust spent power fluid fromsaid engine; a rod flow passageway means formed from said lower pistonchamber, through said piston, through said valve control rod, and intosaid seal tube flow passageway;

so that when said control rod moves said valve ele ment to the firstposition, power fluid flows from said power fluid inlet, through saidvalve assembly, to said seal tube flow passageway, and to said lowercylinder chamber causing the piston to upstroke while fluid flows saidupper piston chamber, through said valve assembly, and through saidexhaust flow passageway;

and, as the control rod moves up, the valve element shifts to the secondposition, causing power fluid to flow from said power fluid inlet,through said valve assembly, into the upper piston chamber to cause thepiston to downstroke while fluid flows from said lower cylinder chamber,into said seal tube flow passageway, through said valve assembly, andthrough said exhaust passageway.

4. The pump assembly of claim 3 wherein said control sleeve has a lowermarginal length supported by said valve body, said lower marginal lengthsealingly engaging an outer marginal length of said control rod forpreventing fluid flow from said upper cylinder into said valve assembly.

5. ln a fluid actuated pump assembly having a valve assembly, an engine,and a production pump, wherein the valve assembly is flow connected to asupply of power fluid and to an exhaust port in a manner to cause theengine to reciprocate the production pump, so that the pump can producefluid from a fluid bearing strata located downhole in a borehole, theimprovement comprising:

said valve assembly including a body having an axial bore therethrough,said engine having a control rod extending therefrom which isreciprocatingly reccived within the axial bore, a control sleeve, areciprocating valve element; said control sleeve being affixed to saidvalve body; said valve body, said control sleeve, said valve element,and said control rod being concentrically arranged relative to oneanother with a marginal length of said rod being slidably received insealed relationship respective to a marginal length of said controlsleeve and spaced from said valve element;

said valve element having a marginal length which sealingly engages thesurface of the axial bore and a marginal length which sealingly engagesa marginal exterial surface of said control sleeve so that a variableannular fluid chamber is jointly formed by the valve body, controlsleeve, and valve element; means forming a power fluid inlet chamberwithin said valve element;

means on said control rod for alternately connecting said variableannular chamber to said exhaust port and to said power fluid inletchamber in response to reciprocation of the engine for causing saidvalve element to reciprocate between a lowermost and an uppermostposition;

a spiral groove forming a controlled flow passageway between said valveelement and said control sleeve for flow of power fluid from said powerfluid inlet chamber into said variable annular fluid chamber when saidvalve element is reciprocated into an uppermost position;

means forming a bleed port for connecting said variable annular tluidchamber to said exhaust port when said valve element is in a lowermostposition;

said controlled flow passageway being spaced from said power fluidchamber by said marginal surface of said control sleeve which sealinglyengages said valve clement when said valve element is in a lowermostposition, so that leakage of power fluid across the last recited sealingsurfaces is exhausted from said variable annular fluid chamber;

and means by which said valve element causes said valve assembly toalternately connect the power fluid passageway and the exhaust port ofthe engine to the power fluid inlet passageway and to the exhaust portof the valve assembly as the valve element reciprocates.

6. The improvement of claim 5 wherein said spiral groove is provided onthe marginal longitudinal interior surface of said valve element whichslidably contacts said marginal exterior surface of said control sleeveto provide for a bleed passageway through which power fluid can flow.

1. A fluid actuated pump assembly having a valve assembly, a power fluidchamber, an engine, and a production pump, a formation fluid inlet flowmeans and a produced fluid flow means flow attached to said pump; meansby which a source of power fluid can be flow connected to the powerfluid chamber of the valve assembly; and a spent power fluid outlet; theimprovement comprising: said engine having a piston reciprocatinglyreceived within an engine cylinder, said piston dividing said enginecylinder into an upper cylinder chamber and a lower cylinder chamber; avalve control rod having an axial flow passageway formed therethrough,said control rod being connected to said piston and extending throughthe valve assembly for controlling the action of the valve assemblywhich in turn controls the fluid flow path to said engine; a seal tubesupported by said valve assembly and spaced from said control rod, saidcontrol rod being received within said seal tube; seal meansreciprocatingly receiving said control rod therethrough for preventingpower fluid flow from the power fluid chamber, along the exteriorsurface of the rod, and into said seal tube; a connecting rod connectedbetween said piston and the production pump for actuating the productionpump; means forming a first flow passageway from the valve assembly tosaid upper cylinder chamber, means forming a second flow passageway fromthe valve assembly to the interior of said seal tube, and into theinterior of said hollow valve control rod, through said piston, and intosaid lower cylinder chamber; means forming an exhaust flow passagewaythrough which spent power fluid from the engine can flow; said valveassembly includes a control sleeve axially aligned with andreciprocatiNgly receiving said control rod therethrough; a valve elementconcentrically arranged respective to said control rod and said controlsleeve and movable from a first to a second position, a marginal lengthof said control sleeve being received within a marginal length of saidvalve element; spaced shoulders on said valve element forming atraveling annulus for flow connecting said exhaust passageway to saidsecond passageway when said valve element is in the first position, andfor flow connecting said exhaust passageway to said first passagewaywhen said valve element is in the second position; a spiral grooveformed on a marginal longitudinal interior surface of said valve elementwhich slidably contacts said marginal exterior surface of said controlsleeve to provide for a bleed passageway through which power fluid canflow; so that said valve assembly connects said first flow passageway tosaid exhaust flow passageway for conducting spent power fluid away fromsaid upper chamber; and to conduct power fluid flow to said second flowpassageway in order to cause said piston to reciprocate in a firstdirection; and, said valve assembly connects said first flow passagewayto conduct power fluid flow to said upper chamber and to conduct spentpower fluid flow away from said second flow passageway in order to causesaid piston to reciprocate in a second direction.
 2. The pump assemblyof claim 1, wherein said control sleeve has a lower marginal lengththereof supported by said valve body, said lower marginal lengthsealingly engaging an outer marginal length of said control rod forpreventing fluid flow from said upper cylinder, along the exteriorsurface of the rod, and into said valve assembly.
 3. A fluid actuatedpump assembly comprising a valve assembly, a fluid actuated engine, anda production pump; said valve assembly providing flow control means forsaid engine and including a valve body, a traveling valve elementreciprocatingly received within said body and movable between a firstand second flow control position, an axial passageway formed throughsaid valve element; said engine having a cylinder, a pistonreciprocatingly received within said cylinder and forming upper andlower cylinder chambers; a valve control rod attached to said piston andhaving a marginal free end portion extending through said axialpassageway, a power fluid flow passageway formed between said rod andsaid valve element; means forming a power fluid inlet which is in flowcommunication with said power fluid flow passageway; a seal tube forreciprocatingly receiving a free marginal length of said control rod andforming a flow passageway therebetween; a seal means separating saidpower fluid flow passageway from said seal tube flow passageway, a flowpassageway formed from said power fluid flow passageway to said sealtube flow passageway; said valve control rod having means associatedwith said power fluid flow passageway for causing said valve element toassume said first flow position and said second flow position inresponse to reciprocation of said piston; said valve assembly includes acontrol sleeve axially aligned with and reciprocatingly receiving saidcontrol rod therethrough; said valve element being concentricallyarranged respective to said control rod and said control sleeve with amarginal length of said control sleeve being received within a marginallength of said valve element; spaced shoulders on said valve elementforming a traveling annulus for flow connecting said exhaust passagewayto said second passageway when said valve element is in the firstposition; said valve element is provided with a spiral groove on themarginal longitudinal interior surface which slidably contacts saidmarginal exterior surface of said control sleeve to provide for a bleedpassageway through which power fluid can flow; a flow passageway meansflow connecting said upper cylinder chamber with said valve element; Aflow passageway means flow connecting said seal tube flow passagewaywith said valve element; an exhaust flow passageway means connectingsaid valve element to exhaust spent power fluid from said engine; a rodflow passageway means formed from said lower piston chamber, throughsaid piston, through said valve control rod, and into said seal tubeflow passageway; so that when said control rod moves said valve elementto the first position, power fluid flows from said power fluid inlet,through said valve assembly, to said seal tube flow passageway, and tosaid lower cylinder chamber causing the piston to upstroke while fluidflows said upper piston chamber, through said valve assembly, andthrough said exhaust flow passageway; and, as the control rod moves up,the valve element shifts to the second position, causing power fluid toflow from said power fluid inlet, through said valve assembly, into theupper piston chamber to cause the piston to downstroke while fluid flowsfrom said lower cylinder chamber, into said seal tube flow passageway,through said valve assembly, and through said exhaust passageway.
 4. Thepump assembly of claim 3 wherein said control sleeve has a lowermarginal length supported by said valve body, said lower marginal lengthsealingly engaging an outer marginal length of said control rod forpreventing fluid flow from said upper cylinder into said valve assembly.5. In a fluid actuated pump assembly having a valve assembly, an engine,and a production pump, wherein the valve assembly is flow connected to asupply of power fluid and to an exhaust port in a manner to cause theengine to reciprocate the production pump, so that the pump can producefluid from a fluid bearing strata located downhole in a borehole, theimprovement comprising: said valve assembly including a body having anaxial bore therethrough, said engine having a control rod extendingtherefrom which is reciprocatingly received within the axial bore, acontrol sleeve, a reciprocating valve element; said control sleeve beingaffixed to said valve body; said valve body, said control sleeve, saidvalve element, and said control rod being concentrically arrangedrelative to one another with a marginal length of said rod beingslidably received in sealed relationship respective to a marginal lengthof said control sleeve and spaced from said valve element; said valveelement having a marginal length which sealingly engages the surface ofthe axial bore and a marginal length which sealingly engages a marginalexterial surface of said control sleeve so that a variable annular fluidchamber is jointly formed by the valve body, control sleeve, and valveelement; means forming a power fluid inlet chamber within said valveelement; means on said control rod for alternately connecting saidvariable annular chamber to said exhaust port and to said power fluidinlet chamber in response to reciprocation of the engine for causingsaid valve element to reciprocate between a lowermost and an uppermostposition; a spiral groove forming a controlled flow passageway betweensaid valve element and said control sleeve for flow of power fluid fromsaid power fluid inlet chamber into said variable annular fluid chamberwhen said valve element is reciprocated into an uppermost position;means forming a bleed port for connecting said variable annular fluidchamber to said exhaust port when said valve element is in a lowermostposition; said controlled flow passageway being spaced from said powerfluid chamber by said marginal surface of said control sleeve whichsealingly engages said valve element when said valve element is in alowermost position, so that leakage of power fluid across the lastrecited sealing surfaces is exhausted from said variable annular fluidchamber; and means by which said valve element causes said valveassembly to alternately connect the power fluid passageway and theexhaust port of the engine to the power fluid inlet passageway and tothe exhaust port of the valve assembly as the valve elementreciprocates.
 6. The improvement of claim 5 wherein said spiral grooveis provided on the marginal longitudinal interior surface of said valveelement which slidably contacts said marginal exterior surface of saidcontrol sleeve to provide for a bleed passageway through which powerfluid can flow.